Droplet ejecting devices are used for various industrial purposes, an example of which is forming film of a polymeric material for use as luminescent layer material of organic EL.
A droplet ejecting device generally has a droplet ejecting mechanism called a “head”, and has a configuration wherein a plurality of nozzles are arranged in a particular order at the head and a liquid is ejected through the nozzles in a form of droplets.
Generally, the diameter of a nozzle for ejecting a droplet is extremely small. Accordingly, nozzle clogging resulting from the viscosity of a liquid to be ejected is, to some extent, inevitable. A clogged nozzle left unchecked, can in an extreme case cause a so-called dead pixel phenomenon, where no droplet can be ejected via the nozzle. To avoid product deterioration directly caused by the dead pixel phenomenon, a conventional droplet ejecting device uses a laser beam for determining whether a nozzle is clogged, by detecting a change in luminous energy of the laser beam which is caused when a droplet falling from a nozzle intersects the laser beam.
In this conventional method, however, it is difficult to install a laser accurately enough that a path of a falling droplet intersects the laser beam. In addition, since it is necessary to eject a plurality of droplets per nozzle to make an accurate detection, and since nozzle clogging is detected while a head or a detection device is moving, the process becomes complex and, furthermore, in a case where a liquid to be ejected is very expensive, cost becomes a significant factor.